Rhesus monkeys that were exposed to PCB three years previously and still exhibiting ill effects from this exposure will be evaluated for a 4th year to determine if these deleterious effects persist, particularly in their offspring. In addition to reduced birth weights and neonatal growth rates, these infants have shown inhibited learning and behavioral development. A second group of rhesus monkeys that have been fed PCBs for 1 year at levels that are close to what heavy fish-eating humans may consume, will continue the exposure for a second year. Emphasis will be placed on the cumulative effects that may arise from long term, low level exposure in the adult monkey, as well as the injurious effects that may arise in their offspring. In other experiments, infants born to rhesus mothers that were exposed to levels of PCB (Aroclor 1016) as low as 25 ppb for one year will be evaluated psychologically for learning and behavioral development. Since these infants have shown gross signs of PCB intoxication, the potential effects on the development of the central nervous system is of prime importance. The question invariably arises as to the difference in response that may be experienced by man and lower animals to commercial preparations of PCB vs. PCB that is present in the food chain. Fish oil containing PCB will be extracted from fish and placed in the diet of rhesus monkeys at levels similar to that utilized in experiments where commercial PCB preparations were used. These animals will be evaluated as to the effects this diet has on the adult monkey and its offspring. These data will then be compared with that obtained in experiments that have used commercial PCB mixtures in the diet.